My New Year gift to TW: A new theremin circuit

Hi everyone! I'm starting to do this as my school project, but I don't get it, from where I can order proper antenna? I mean, like what kind of antenna is it, RF, tube, which frequency (center/band)  etc? I'm so troubled when trying to find appropriate one i.e from digikey  . 

hi melluxx,

don't worry too much about the antenna....Ø=6mm,L=~50cm...you need a simple one like this: antenna . you could easily salvage one from a broken radio or something.

Thierry, I just built your circuit design, and wow, this works better than I could have hoped!  My first theremin!  My 12 yo daughter and I had a lot of fun playing with it last night, as she repeatedly exclaimed "This is really cool!"   Thank you!

I've included a few photos below.  I included an LM386 amplifier and a small 2W speaker, and designed a 3D printed case for it.  I have discovered it works best when grounded, so have also added a grounding plug for use when not connected to an external amplifier (and grounded through the 1/4" connector shield). 

I do have one question though...  In your tuning instructions, you state that the coarse and fine tuning should be used to achieve "a pleasant field geometry and tone spacing".  I haven't played with a theremin before, so not sure what I should be looking for.  Is there a target frequency when, say, I am standing a meter away from the theremin?  And how many octaves higher should I expect when placing my hand a few inches from the antenna? 

Ok, some photos...

"I've included a few photos below.  I included an LM386 amplifier and a small 2W speaker, and designed a 3D printed case for it.  I have discovered it works best when grounded, so have also added a grounding plug for use when not connected to an external amplifier (and grounded through the 1/4" connector shield)."

I really like the case that you designed. I am attempting to build some for a physics demo for school project. Is there some way I could get the design to print one off for myself?

"I really like the case that you designed. I am attempting to build some for a physics demo for school project. Is there some way I could get the design to print one off for myself?"

Sure Randolph!  I have posted the 3D printed case and amplifier schematic on Thingiverse:

https://www.thingiverse.com/thing:2783670

I've done my best to list all the specific parts needed to fit in the case.  Breadboard size, rocker button, and speaker diameter are all important.  I was able to find everything on Amazon and Mouser, except for the JFETs which I got off eBay for a reasonable price. 

This will make a great physics demo!  Turn your body into a human capacitor!  And the math showing the resonant frequencies of the two oscillators and beat frequency would make a great lesson. 

Let me know if you have any question on the construction of the case.

Hi, my first post as a newbee,

I have been struggling with the Weird apparatus /wine box theremin design for some time now, after reading all the posts i think my error is using vero strip to build on i get some pitch varaution but canot get the VC amplifier to respond despite getting a couple of volts variation from hand gestures at the gate of fet1.

So in order to make progress i am starting again with a pitch only design

I and am taken by the simplicity of the Thierrymin, I wonder if anyone produces the PCB for sale, my days of messing with baths of ferric chloride and way distant memories now and i have not found a source of dot veroboard, I live in the UK.

If anyone knows a source I would appreciate a point in the right direction, many thanks Steve

Hi Steve,

I do not have Thierrymin PCBs actually. But I remember having given some to the Dutch Thereminist Wilco Botermans for a project, last year and he might have some left over. You may try to contact him via his website ethermagic.eu :)

Hi Thierry
Thank you for the quick reply, i will contact Wilco in the hope has has not used them all.
Best regards
Steve

Hello everyone,

I've watched a YouTube video by Keystone Science and come across this circuit, and tried to reproduce it. However, when I connect the speakers, I either hear noise or silence; the noise is very loud and randomly triggered, and often fixed by just touching (without even moving) a specific jumper cable (the green one in the photo, connecting the mixer JFET to the antenna).

The connections I've made should be fine. I checked them, then disassembled and reassembled the circuit twice. Here's some detail about the differences between my circuit and the one from Thierry's original post. (Surely they are possible reasons why my theremin wouldn't sound exactly like his, but how reasonable it is that they are making it even not work at all?)

- I am building it on a breadboard (besides, I'm reading that many other people have used a breadboard too...)
- I am using a power supply module that came out with my Elegoo kit (very similar to this one; both ends are set to 5V (my DMM reads 4.93V between the two rails of the breadboard), so I didn't use the voltage regulator around V31. Connecting the circuit directly to a 9V battery makes no difference, by the way.
- The capacitor that I'm using as C44 reads only "3" on it; I assume it's 3.3pF since the set of capacitors I have bought contains all other 10-multiples of 3.3pF (would 0.3pF matter anyway?)
- Since I couldn't buy 2N5484 JFETs, I used 2N5457's instead (yeah, I hadn't read all of this thread when I bought them... but still, will this completely compromise the circuit?)
- I have soldered some 25~30cm of copper cable to the antenna, which is ~60cm long. The cable is directly inserted into the breadboard.
- To make audio output I've used a jack socket that has three pins: one of the short ones is connected to C23, while the other two are grounded. With this jack plug I have connected the circuit to a Behringer preamp (which works just fine with anything else*), and the output of the latter is connected to a speaker.

I'm attaching also a picture of it. I hope someone can tell me if I did something wrong, or some tests I can do to check the circuit (unfortunately I have no oscilloscope). Thank you in advance!

* You can see in the photo a red jumper cable going to another jack cable. That is connected to my iPod, playing some music. Moving the jumper cable from C23 to there, I can listen to my music without any problem.

I am not very active but dislike lonely threads.

I can not help you as I have never put together this design and not psychic. It is too bad an iron-on PCB layout was not drawn up and made available by one of the many builders of this circuit. Home PCB making is a good thing to learn. I would never recommend construction of a high frequency analog project like this on one of those white proto boards due to unwanted capacitance coupling between components. I have known of one person that builds this way but he has experience to do this, but then again he has never really demonstrated anything that works. In theremin design an ugly sound vs a beautiful sound are only separated by a thin margin of knowledge. Where you found your inspiration for this design constructed this way, was the sound good? I would call that a happy theremin one that was not stressed.

T

Edit: Just saw the video, the last 30 seconds was best with his 2 meters of wire stuffed inside the case for tuning, I think of the theremin as an illusion and that builder takes it to another level.